The invention relates to methods for regenerating metal and metal oxide hydrogen sulfide sorbents by treating the spent sorbents with an oxidizing atmosphere following by a reducing atmosphere. The sorbents may be mono- or multi-metallic in nature.
The removal of sulfur from feedstocks is a fundamental process of the refining and petrochemical industries. One process for removing sulfur from a feedstock is hydrodesulftirization. Hydrodesulfurization involves the reaction of sulfur in the feedstock with hydrogen over noble metals, such as Pt, Pd, or non-noble metal sulfides, especially Co/Mo and Ni/Mo catalysts, at fairly severe temperatures and pressures to form hydrogen sulfide. The performance of the hydrodesulfurization catalysts can be inhibited by the presence of hydrogen sulfide. The use of sorbents to remove the hydrogen sulfide produced during the reaction improves the effectiveness of the overall hydrodesulfurization process.
The performance of a hydrogen sulfide sorbent depends on a variety of properties. Thermodynamics and kinetics of sulfidation clearly are important, because they determine the overall sulfur capacity before breakthrough at some predetermined level of H2S. Other important sorbent properties include stability and regenerability in extended use, the operating conditions required for regeneration, and the composition of the regeneration off-gas, which largely determines the choice of a downstream sulfur recovery process.
A practical limitation on the use of any hydrogen sulfide sorbent is the ability to regenerate the sorbent. The scope and applicability of such sorbents is limited by economic constraints relating to the level of sulfur being processed, the reactor volumetrics required, and issues pertaining to removal and disposal of the spent sorbent. These limitations are relieved if the sulfur sorbent is capable of multicycle operation made possible by a means for regenerating the sorbent material.
The present invention provides a process for regenerating a hydrogen sulfide sorbent comprising providing a spent hydrogen sulfide sorbent containing metal or metal oxide wherein the metal is at least one of Fe, Ni, Cu, Co, and Zn. Fresh hydrogen sulfide sorbent may be characterized by a level of sulfur defining a first cycle capacity for absorbing hydrogen sulfide. The spent hydrogen sulfide sorbent may be regenerated by first exposing it to a gas comprising a regenerating concentration of an oxidizing gas under conditions effective to oxidize said spent hydrogen sulfide sorbent. The oxidized hydrogen sulfide sorbent is then exposed to a gas comprising a regenerating concentration of a reducing gas under conditions effective for the gas to regenerate the spent hydrogen sulfide sorbent, thereby producing a regenerated sorbent having an effective regenerated capacity for sulfur.